route "earliest" to first shard

also, prevent uint64 conversion underflows by routing any other block tag
that is encoded to a negative number to the default proxy

main_test.go

@@ -441,10 +441,10 @@ func TestE2ETest_HeightBasedRouting(t *testing.T) {
 			expectRoute: service.ResponseBackendShard,
 		},
 		{
-			name:        "request for earliest height -> default",
+			name:        "request for earliest height -> 1st shard",
 			method:      "eth_getBlockByNumber",
 			params:      []interface{}{"earliest", false},
-			expectRoute: service.ResponseBackendDefault,
+			expectRoute: service.ResponseBackendShard,
 		},
 		{
 			name:        "request for latest height -> pruning",

service/shard.go

@@ -129,12 +129,24 @@ func (sp ShardProxies) ProxyForRequest(r *http.Request) (*httputil.ReverseProxy,
 	}
 
 	// parse height from the request
-	height, err := decode.ParseBlockNumberFromParams(decodedReq.Method, decodedReq.Params)
+	parsedHeight, err := decode.ParseBlockNumberFromParams(decodedReq.Method, decodedReq.Params)
 	if err != nil {
 		sp.Error().Msg(fmt.Sprintf("expected but failed to parse block number for %+v: %s", decodedReq, err))
 		return sp.defaultProxies.ProxyForRequest(r)
 	}
 
+	// handle encoded block numbers
+	height := parsedHeight
+	if height == decode.BlockTagToNumberCodec[decode.BlockTagEarliest] {
+		// convert "earliest" to "1" so it routes to first shard
+		height = 1
+	} else if parsedHeight < 1 {
+		// route all other encoded tags to default proxy.
+		// in practice, this is unreachable because they will be handled by the pruning Proxies
+		// if shard routing is enabled without PruningOrDefaultProxies, this handles all special block tags
+		return sp.defaultProxies.ProxyForRequest(r)
+	}
+
 	// look for shard including height
 	url, shardHeight, found := shardsForHost.Lookup(uint64(height))
 	if !found {

service/shard_test.go

@@ -236,18 +236,6 @@ func TestUnitTest_ShardProxies(t *testing.T) {
 			expectBackend: service.ResponseBackendDefault,
 			expectRoute:   archiveBackend,
 		},
-		{
-			// TODO: should it do this? if shards exist, route to first shard?
-			name: "routes to default for 'earliest' block",
-			url:  "//archive.kava.io",
-			req: &decode.EVMRPCRequestEnvelope{
-				Method: "eth_getBlockByNumber",
-				Params: []interface{}{"earliest", false},
-			},
-			expectFound:   true,
-			expectBackend: service.ResponseBackendDefault,
-			expectRoute:   archiveBackend,
-		},
 
 		// PRUNING ROUTE CASES
 		{
@@ -305,6 +293,17 @@ func TestUnitTest_ShardProxies(t *testing.T) {
 		},
 
 		// SHARD ROUTE CASES
+		{
+			name: "routes to 1st shard for 'earliest' block",
+			url:  "//archive.kava.io",
+			req: &decode.EVMRPCRequestEnvelope{
+				Method: "eth_getBlockByNumber",
+				Params: []interface{}{"earliest", false},
+			},
+			expectFound:   true,
+			expectBackend: service.ResponseBackendShard,
+			expectRoute:   shard1Backend,
+		},
 		{
 			name: "routes to shard 1 for specific height in shard 1",
 			url:  "//archive.kava.io",